US3468488A

US3468488A - Automatic control of feed material in a comminuting mill

Info

Publication number: US3468488A
Application number: US510626A
Authority: US
Inventors: Karl Karrer; Robert Linzberger
Original assignee: Buehler AG
Current assignee: Buehler AG
Priority date: 1965-11-30
Filing date: 1965-11-30
Publication date: 1969-09-23
Anticipated expiration: 1986-09-23

Description

Sept. 23, 1969 KARRER ETAL 3,468,488

AUTOMATIC CONTROL OF FEED MATERIAL IN A COMMINUTING MILL Filed Nov. 30, 1965 2 Sheets-Sheet l a vlvlllrtllrlllanallcvlacod KHRL KHRRER ROBERT LIA/2551965? Sept. 23, 1969 K. KARRER ETAL AUTOMATIC CONTROL OF FEED MATERIAL IN A COMMINUTING MILL Filed Nov. 30, 1965 2 Sheets-Sheet 2 VENTORS KARL KRRRER ROBERT LINZBERGER r MMMM W United States Patent 3,468,488 AUTOMATIC CONTROL OF FEED MATERIAL IN A COMMINUTING MILL Karl Kan-er, Wil, and Robert Linzberger, Bruggen, S t.

Gall, Switzerland, assiguors to Gebruder Buhler, UZWll, Switzerland Filed Nov. 30, 1965, Ser. No. 510,626

Int. Cl. B02c 4/32, 7/14, 9/04 US. Cl. 241-34 11 Claims ABSTRACT OF THE DISCLOSURE A device for feeding material in a roller mill includes a mill frame housing with a relatively wide feeding portion and with a relatively narrow cross infeed conduit arranged centrally of the housing to feed material down into the housing between a pair of cooperative grinding rollers which are located below the infeed conduit. The rollers may be displaced outwardly relative to each other in order to provide for more rapid feeding therebetween as one means of feed regulation. In addition, a feed roller is mounted in said housing between the grinding rollers and the infeed conduit and it may be moved backwardly and forwardly in respect to a gate valve for varying the feed opening therebetween. A feature of the construction is that spaced capacitor plates are located in the infeed conduit and they are electrically connected for continuously sensing the material being fed therepast in the infeed conduit. The plates are electrically connected in a control circuit either to the grinding rollers for the purposes of displacing the grinding rollers are apart or moving them inwardly toward each other in response to change in feed conditions in the feed conduit, or to either the feed roller or the gate valve for varying the spacing therebetween. A further or an independent variation of feed control may be eifected by changing the speed of the gate valve feed roller or the grinding rollers.

This invention relates to devices for feeding and treating bulk material and to a method of operating the feed therefor and, in particular, to a new and useful mill roller frame having a measuring and control device for effecting the various roller frame functions and to a method of feeding material through such roller frame.

Up to the present time, it has been known to use socalled Christmas trees or structures of rods which are suspended above the roller elements for the control of mill roller frames. A propeller secured on a lever has been used successfully for controlling at least the feeding device of the roller frame. Such a propeller has a tendency to work always toward the surface of the feed cone. All of the devices of the prior art have the disadvantage that because of the certain hysteresis which occurs in the indication they have a considerable susceptibility to fouling. Because the indicating elements must transmit the measured values mechanically to an evaluating device, the sensitivity is not very great and considerable energy must be expended for the control.

In accordance with the invention, a new roller frame is provided which is characterized by the provision of an electrocapacitance feed flow meter which is provided in the feed flow for controlling at least one roller frame function. A particular advantage of the capacitative-type of How meter of the present invention is that there is no hysteresis because it operates on an electrocapacitance basis. In addition, the energy required for effecting control is very slight since the electrostatic displacement flow in the range of the capacitor has a negligible influence on the material flow.

In accordance with a preferred arrangement of the in- Patented Sept. 23, 1969 vention, the mill roller includes an entrance feed passageway in which are located an electric capacitor comprising two plates separated by insulation which are separately connected to a control device and which includes means for measuring the change in capacitance produced by the flow of material through the entrance passageway past the plates. The material then passes between a rotating feed roller and a control gate or valve which may be regulated individually or together in order that the material height at a location directly before the main rollers may be separately controlled. The main grinding rollers are located directly below the incoming feed roller at a location directly above a discharge chute. In a preferred arrangement of the invention, initial control of the feed of the material is made before the feed roller and the entrance gate by measuring the changes of height of the feed stack at such location through the capacitor indication and by adjusting the feed roller speed and/or the gate or position to permit more or less feed flow in accordance with the desired height of material which is desired. In an improved method of operating, the material is permitted to fiow downwardly in the entrance passage to the feed roller and entrance gate and the capacitor is used to sense the height of the material and to adjust the feeding part of the gate and feed roller in accordance with the height of material sensed.

The apparatus of the invention further includes means for mounting at least one of the main mill or grinding rollers so that it may be moved toward and away from the opposite roller. The eleetrocapacitance control is connected to means for shifting the roller when insufficient material is being delivered through the incoming passageway. The control also advantageously includes means for indicating the amount of material which is flowing through as shown by variations of the capacitor current values which are obtained.

Accordingly, it is an object of the invention to provide an improved mill roller frame having electrocapacitance means for measuring and controlling the feed thereto.

A further object of the invention is to provide a mill roller frame which includes two large mill rollers rotatably mounted over a discharge chute with at least one of the rollers being movable toward and away from the other roller to vary the spacing therebetween, and with an entrance passageway located above the rollers which directs the incoming feed material downwardly between a feed roller and a gate member which may be separately and individually controlled for varying the feed of material therebetween; and including an electrocapacitance flow control means located in the incoming passage for measuring the height of the material being heaped before the feed roller and measuring the flow rate through the passageway and for indicating this flow rate; and for controlling the speed of rotation of the feed roller and/ or the opening of the gate valve in accordance with the amount of material which is being sensed.

A further object of the invention is to provide a method of operating a mill roller frame which includes directing the materials to be treated into an inlet passageway having a capacitative flow measuring means therein, permitting the material to be flown between a rotating feed roller and a gate valve downwardly onto mill rollers which are movable toward and away from each other and regulating the rotation of the feed roller and the opening of the gate valve in accordance with the feed of the material which is sensed in the entrance passageway, and for separating the main rollers when the feed level is insuificient.

A further object of the invention is to provide a mill roller frame which is simple in design, rugged in construction and economical to manufacture.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described preferred embodiments of the invention.

In the drawings:

FIG. 1 is a partly schematic transverse sectional view of a mill roller having a flow indicating and control device constructed in accordance with the invention;

FIG. 2 is a partial sectional view taken on the line II-II of FIG. 1; and

FIG. 3 is a view similar to FIG. 2, but of another embodiment of the invention.

Referring to the drawings, in particular, the invention embodied therein FIGS. 1 and 2 comprises a housing generally designated 1 of a mill roller frame in which is arranged a fixed roller 2 and an adjustable roller 3. The roller 2 is rotatably mounted on end portions of the housing 1 and the roller 3 is rotatably mounted on a rocker element 11 which is pivoted at 12 to a supporting bracket 10. In accordance with one feature of the invention, the roller 3 may be moved toward or away from the roller 2 by rotating the element 11 which is connected to a connecting rod 17 having a piston portion 15 which is slidable in a fluid cylinder 16. The rod portion 17 is connected to the element 11 through a connecting member 11a and a spring 18. Adjustment of the position of the member 11 is accomplished by the supply of fluid under pressure through a conduit 78 under the control of a throttle valve 76. In the position indicated in FIG. 1, the piston portion 15 is shown to the left of the cylinder and the element 11 is held in a position at which the roller 3 engages the roller 2. The nip between the rollers 2 and 3 is located directly above a discharge opening 21 in the housing and baffle plates 22 are inclined over the opening to direct the material therethrough.

Rotatably mounted above the rollers 2 and 3 is a feed roller which cooperates with a feed valve or gate member 6. The gate 6 is mounted for pivotal movement about a pivot 29 in order to control the opening between the gate 6 and the roller 5. The valve 6 may be pivoted by moving a crank lever member 28 to which it is attached. This movement is effected through a piston 25 which is displaceable in a fluid cylinder 26 to cause the displacement of a rod portion 27 which is connected to the crank lever 28 through a spring 30. Control of the position of the piston 25 and the cylinder 26 is made through a fluid control line 68 under the control of a movable element 62a of a throttle valve 62.

The inlet to the roller frame is through an inlet means or inlet pipe 4 which is arranged directly over the rollers 2 and 3 and above the feed roller 5 and inlet gate 6. The inlet means 4 includes at its lower end a widened portion in which is located, in accordance with the invention, capacitor plates 31 and 33 of an electrocapacitance feed flow meter. The base plate 31 is connected with the mill roller frame and carries insulation 32. A probing plate 33 is mounted on the exterior of the insulation 32. in the passageway 4 at the location of the incoming feed of material being fed.

The device is particularly applicable for feeding nonmetallic products such as granular, gritty, or mealy, bulk goods but not for pasty products. A baflle 110 is advan tageously located in the pipe in order to deflect the material outwardly over the plates 31 and 33 through a chamber 112 formed directly over a baffle plate 114 located on the opposite wall of the pipe 4 from the plate 33. In the embodiment of FIGS. 1 and 2, the plate 33 extends over the complete width of the space 112 and the electrocapacitative displacement flow takes place from the probing pole 33 to the opposite roller frame housing wall.

4 The probing pole 33 and the base plate 31 are con- 'nected through corresponding

electrical conduits

43 and 41 with an amplifying measuring and control device generally designated 40. The amplifying, measuring and control device 40 is connected with a suitable source of current at 50. It includes suitable amplifier and transformer means (not shown) for detecting an indication of the change of capacitance between the plates 32 and 33 as a result of the material which is present in the delivery passage of the conduit 4. These indications of changes of capacitance are measured and indicated as a flow rate on a flow rate indicator 45. A feature of the invention is that the control means 40 also includes means for controlling the initial feed from the passage 4 to the rollers 2 and 3 by regulating the speed of the roller 5 and the opening of the gate 6 and the feed between the rollers 2 and 3 by controlling the amount of separation thereof. For this purpose the control means 40 includes control indicator setting means 83, 97 and 93 for setting various values at which suitable electrical, mechanical or pneumatic controls will be operated for eifecting the control of the feed of the material as desired.

In accordance with the invention, suitable means are provided for effecting the shifting of the

pistons

15 and 25 in order to shift the position of the roller 3 and the gate valve 6 as desired. In the embodiment illustrated, a pneumatic system is provided which is fed through a blower 60. Connected to the blower 60 is a fluid pressure line 61 which branches into the throttle element 62 having a movable setting element 62a which is controlled by an electromagnet or solenoid 63. The solenoid 63- is connected through lines 84 to the adjustable setting means 83 which is set for the actuation of the solenoid 63 at a desired sensed current. Another branch of the pressure line 61 leads to a shutoff element 72 or valve with an associated solenoid actuator or magnetic coil 73. Current for the coil 73 is supplied through lines 94 having a relay switch 95 therein. In accordance with the capacitance amount sensed by the plates 31 and 33, the switch 95 will be thrown by suitable electromagnetic means in the control 40 (not shown) to cause current to flow through the lines 94 to actuate the solenoid 73.

The operation of the device is as follows: The material to be ground enters the roller frame through the conduit 4. In the chamber 112 above the feed roller 5 and the gate valve 6, the material will begin spreading outwardly along the stacked lines indicated 101, 102 and 103 in FIG. 2. The height of the stacked material above the feed roller 5 will approach one of the solid or dotted line indications in accordance with the feed through the conduit 4 and the speed of rotation of the feed roller 5 and the opening of the gate valve 6. In this manner, the probing pole 33 which is connected through the line 43- to the measuring and control device 40 will sense the material in the chamber 112 to cause a high frequency voltage to be generated which is in proportion to the material located therein. The plate 31 is connected to ground potential so that an electrocapacitance displacement flow between the probing pole 33 and the opposite roller frame housing is effected. This capacitance displacement flow is influenced by the entering material which as indicated forms into a cone. Depending upon whether a large amount of material with the resulting cone 103 is formed or a small amount with resulting

cones

102 or 101, the displacement flow is influenced and this influence, that is, the variation of flow yields in a known manner a variation of voltage. The variation of voltage is used in the control arid measuring device 40 to actuate the throughput of flow indicator 45 and, after sufficient amplification'and transformation, to actuate roller frame control elements. In some instances it is desirable that these measured values are employed directly to influence the working apparatus or connected through suitable pneumatic or hydraulic working elements and electrical apparatus in order to control the working elements. In the present instance, an electro pneumatic control system is shown and the electrical measuring values serve to control pneumatic control elements which, in turn, control pneumatic working elements.

The following three controls are provided with the invention (1) an idle run supervision, (2) control of the feed valves and feed rollers, respectively, and (3) control of the roller gap. At any time during the operation of the mill, it is important that when no material enters the roller frame through the conduit 4, the main rollers 2 and 3 must be immediately pulled apart. The electrocapacitance measuring device will in such instance produce a voltage in the feed flow meter 45 showing in sufficient material and which will cause the reversal switch 95 to be actuated to move from the rest position into the operation position. When this occurs, the current is passed through the lines 94 to the solenoid 73 to shut oil the pneumatic flow control element 72. The time at which this happens, of course, is set by the adjustable setting means 93. When the valve element 72 is closed, there is no fluid pressure directed through the line 75 to the throttle 76 and through the line 78 to the cylinder 16. This permits the piston 15 to move backwardly in the cylinder 16 and permit the spring 18 to relax to permit the rocker element 11 to move backwardly to cause separation of the roller 3 from the roller 2 so that the feed can no longer suffer any damage when feeding fails.

There are two possibilities for the controlling of the feed, the gate valve 6 may be opened or closed in a desired amount and, in addition, a second means is the regulation of the speed of the feed roller 5. A still further control would be effected by a regulation of each of these elements.

As indicated in FIGS. 1 and 2, depending on the amount of material to be ground, a different covering is obtained in the range of the capacitative measuring device by the probing pole 33 and the housing 1 in accordance with the height of material which is stacked above the feed roller 5 and the gate valve 6. Because of the different heights of material, the dilferent voltages are produced in the controlled measuring device. These voltages are used for regulating the position of the gate valve 6. An accurate control of the position of this valve may be made by first setting the means '83 for controlling the position thereof to a desired amount which will cause current generated by the capacitance indication to flow through the lines 84 to the solenoid 63. The voltages employed for regulating the feed valve are sufliciently amplified in order to cause an actuation of the solenoid 63 and positioning of the throttle 62 as desired. Depending on the degree of opening of the movable elements 62a, a piston 25 in the cylinder 26 will be accurately located. This, in turn, causes an accurate positioning of the gate valve 6 and the control of the feed between the gate valve and the roller 5. This new measuring arrangement has a great advantage that not only the control of the idle run but also the feed control can be automated.

A still further control is the regulation of the roller gap between the grinding rollers 2 and 3. The voltage delivered to the measuring and control device 40 in dependence on the amount of feed is amplified and transformed by the device 40 and the desired control setting may be adjusted by the adjusting device 97. When variations of the set amount occur, current is passed through the line 98 to the solenoid 77 for actuating a movable control element 76a of a control throttle 76. This, in turn, results in a variation of the pressure against the piston 15 for the purpose of regulating the position of the rocker 11 and the roller 3 carried thereby in relation to the roller 2. This variation provides a regulation of the grinding gap as a function of the amount of feed.

In the variation indicated in FIG. 2, there is an automatic electrical control means for regulating the speed of the feed roller. The variable dielectric constant in the range of the capacitance instrument due to variable material currents effects a variable voltage in the control and measuring device 40 which is amplified and transformed by a device 53 which may be set for delivering a desired speed control current through lines 54 to a motor '51 arranged to drive the feed roller 5. This speed control of the roller 5 may be effected both in combination with the control of the feed valve 6 and independently thereof. In some instances an additional control is provided for the control of a cooling fluid through rollers 2 and 3 (not shown).

In so-called double roller frames, where the material to be ground is fed to the two roller frames through a feed pipe 4 and where a division is defined for effecting the two partial paths of feed and two partial currents are produced shortly before the roller frame, a ground pole and a probing pole are arranged centrally so that the electrical displacement currents flow both to the right and to the left. This ensures that with different regulations of both the feed gap between the feed valve 6 and the roller 5 and the grinding gaps between the grinding rollers 2 and 3 satisfactory grinding work will be done without jeoparidizing the grinding rollers of the two paths of rollers arranged in one frame.

It is sometimes advantageous to arrange one or two pole probes at the front of the roller frame in the range of the material inlet or to arrange them in the center of the material inlet with the electrocapacitance displacement flow produced to the right and to the left. This will depend on the control characteristics which is desired. It is also sometimes advantageous to locate the pole probe in the range of the material inlet in a direction perpendicular to the grinding roll axis and toward the material flow.

As indicated in FIG. 3, the assembly of all probes 31, 32' and 33' are arranged to extend perpendicular to the axis of the feed roller 5 rather than parallel thereto as indicated in the other embodiments. Thus, the width of the pole probes is relatively small in respect to the length of the feed roller 5. Such an arrangement, however, has the advantage that any material accumulating in the feed pipe 4' will influence the capacity variation better than when the capacity variation extends over the whole width of the roller frame. The corresponding parts of the invention are designated similar to that of FIGS 1 and 2, but with a prime added.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. A mill roller frame comprising a housing defining a relatively wide feed housing, an infeed conduit for the material to be treated of a smaller dimension than and located centrally above said feed housing, a pair of cooperative grinding rollers located below said infeed conduit in said feed housing, means mounting said grinding rollers below said infeed conduit in said feed housing in a manner permitting relative lateral displacement of said rollers toward and away from each other, a feed roller rotatably mounted in said feed housing between said infeed conduit and said grinding rollers, a gate valve located adjacent said feed roller and displaceable toward and away from said feed roller for varying the feed opening therebetween, and sensing and control means comprising spaced capacitor plates located in said infeed conduit and electrically connected for continlu'ously sensing the material being fd therepast in said feed conduit and connected to at least one of said grinding rollers, said feed roller and gate valve, for selectively varying at least one of the following: the feed opening between said feed roller and said gate valve, the speed of said roller, and the opening between said grinding rollers.

2. A mill roller frame according to claim 1, wherein said one of said capacitor plates is connected to ground potential, and indicator means connected to said capacitor plates for indicating variations in capacitance and therefore the amount of material being fed past said plates.

3. A mill roller frame according to claim 1, including means responsive to the change in capacitance sensed by said capacitor plates to shift said gate valve.

4. A mill roller frame according to claim 1, including means responsive to change of capacitance to shift the said grinding rollers relatively.

5. A mill roller frame according to claim 1, including means responsive to the change in capacitance to change the speed of rotation of said feed roller.

6. A mill roller frame according to claim 1, wherein said sensing and control means includes separate means connected to said gate valve for shifting said gate valve in accordance with change in capacitance sensed by said sensing means and separate means connected to said rollers to shift said rollers toward and away from each other in accordance with change in capacitance sensed, and still further means connected to said feed roller for varying the speed of said feed roller in accordance with the change in capacitance sensed, and means for adjusting the setting of each of said last-mentioned means for changing the actuation of said gate valve, said feed roller and said grinding rollers.

7. A mill roller frame according to claim 1, including a movable pivot member, one of said rollers being mounted on said pivot member and being shiftable with said pivot member toward and away from the other of said rollers, means mounting said gate valve for pivotal movement, and fluid pressure means connected to said pivot member and to said gate valve for shifting said pivot member and said gate valve in accordance with the capacitance sensed by said sensing means.

8. A mill roller frame according to claim 7, wherein capacitance values which are sensed by said capacitance plates are employed for separating said grinding rollers.

9. A mill roller frame according to claim 1, wherein said sensing and control means includes an electrocapacitance feed flow meter including spaced first and second plates separated by insulation located in said infeed conduit, adjacent one wall thereof, the opposite wall forming a counter probe for influencing the capacitance of said plates.

10. A mill roller frame according to claim 1, including first and second capacitor plates separated by insulation and disposed above said feed roller and extending across the complete width of said roller.

11. A mill roller frame according to claim 1, wherein said sensing and control means includes first and second capacitor plates separated by insulation and located above said feed roller and being of a relatively small width in comparison to the width of said feed roller.

References Cited UNITED STATES PATENTS 2,030,448 2/ 1936 Hardgrove 241-34 2,156,736 5/1939 Perry 241-34 X 2,618,395 11/1952 Brabander 22256 2,984,423 5/1961 Roth 241-37 FOREIGN PATENTS 698,084 10/ 1953 Great Britain.

FRANK T. YOST, Primary Examiner US. Cl. X. R. 24l37, 225, 231